oscilloscope integration

[jleightcap]

integrate oscope driver into pipeline.

• [x] libinput interaction per #3
• [x] how to request some fixed number samples
• [x] byte encoding (seem to remember it's just raw data, as in should be the same number for a constant signal)
• [ ] save test signals (/usr/share/test/ocsope-constant.signal, /usr/share/test/oscope-1Hz-sine.signal, etc)
• [ ] validation with signal compiler